PowerPoint? WTF? D:
1. Start -> All Programs -> Accessories -> Paint.
2. Resize the canvas to a size larger than the image you're going to use. Leave enough space for the texts to fit.
3. Choose the black colour, fill the whole image with it.
4. Paste the image, try to align it in the middle horizontally.
5. Choose the white colour and the rectangle tool, make sure it's in the outline mode.
6. Draw rectangles around the image; for 2px border, draw two rectangles without gaps between them.
7. Choose the text tool, set the font to Times New Roman, and set a suitable size. Write up the main title. Then choose the font Arial, a smaller size and write the second line.
8. File > Save As...
9. Write "motivationposterstepbystep.png" in the filename field, choose PNG as the file type. Press Save.
4. How the hell do I center it?
6. How do I make such precise outlines?
4. If you absolutely need to get it right in the middle, then subtract the width of the image from the width of the canvas, divide it by two, then draw temporary lines of that width (should say the length of the line on the status bar when drawing it). Then just paste the image so that it touches both of these lines you drew. (Zoom in a bit to ensure the pixel perfect position.) Fill black over the temporary lines.
6. It's a matter of steady hand really. Again, zooming in may help as long as you can see all corners of the image at once. But Paint's rectangle tool should make perfectly fitting borders, really.